The present invention relates to a sheet supplying device which is able to stack various sized sheets, and to an image forming system in which the sheet supplying device is connected to an image forming apparatus.
A sheet supplying cassette to stack predetermined amounts of sheets is typically provided in image forming systems, such as copying machines and printers, for supplying such sheets. While, for supplying a large number of sheets, a stack of 1000 sheets, for example, a sheet supplying device, being able to stack such a large number of sheets, is connected to a side of the image forming apparatus, whereby the sheets are supplied from this sheet supplying device into the image forming apparatus.
The sheet supplying device comprises a sheet stacking member to stack various sizes of sheets, and which is movable vertically, and alignment members which are movable for positioning the stacked sheets at the proper position for each size of sheets. For positioning the various sizes of sheets in the sheet supplying direction, the edge of the top of a stack of sheets comes into contact with a holding member, such as the interior surface of the sheet supplying device, while the ends of the stacked sheets are aligned by an end edge alignment member, movable in the sheet supplying direction. Further, side edge alignment members are provided to perpendicularly align both sides of the stacked sheets in the sheet supplying direction, and when one of the side edge alignment members is moved, the other member is also driven in conjunction with the former in the opposite direction, whereby the various sized sheets are positioned with their centers being equal each other. In addition, sheet alignment members are known which can be replaced by an operator.
Whichever may be used in the above cases, the end edge alignment member and the side edge alignment member are provided in the sheet supplying device to move horizontally to the sheet stacking member, and both members regulate the position of the stacked sheets from the lowest sheet to the highest sheet. Now, the fundamental sections of the conventional sheet supplying device will be shown in FIG. 7(a).
In FIG. 7(a), sheet stacking member 102 installed in image forming apparatus 101 is able to stack various sizes sheets, and sheet stacking member 102 moves vertically. A sheet stacked in sheet stacking member 102 is conveyed into the image forming apparatus as shown by the arrow. At both sides of sheet stacking member 102, being perpendicular to the conveyance, large empty spaces 102A and 102B are provided, through which side edge alignment members 103 and 104 are extended and move perpendicularly to the sheet conveyance direction. Further, side edge alignment members 103 and 104 move opposite to each other so that interior wall 103A of side edge alignment member 103 and interior wall 104A of side edge alignment member 104 regulate the side edges of the stacked sheets perpendicularly to the sheet conveyance direction.
Further, concerning the sheet conveyance direction, the top edge of the stacked sheets comes into contact with interior wall 101A of image forming apparatus 101. Since large long cavity 102C is formed in sheet stacking member 102, end edge alignment member 105 is ejected through long cavity 102C, and can move in the sheet conveyance direction and reverse to it. Then interior wall 105A of end edge alignment member 105 aligns the end edge of the stacked sheets.
As described above, side edge alignment members 103 and 104 as well as end edge alignment member 105 shown in FIG. 7(a) regulate sheets S1 which is B5 sized sheets and placed longwise, shown in FIG. 7(b).
In order to stack small-sized sheets, such as post cards shown in FIG. 7(c), it is necessary that sheet side edge regulating members 103 and 104 are shifted to the inner positions shown by the double-dashed lines, and end edge alignment member 105 is also shifted to the inner position shown by the double-dashed line in FIG. 7(a). In this case, end edge alignment member 105 can be shifted. However, if side edge alignment members 103 and 104 are shifted to the inner positions shown by the double-dashed lines, distance D1 between long cavity 102C and empty spaces 102A and 102B should be reduced to D2, which is difficult to design from the view point of strength of sheet stacking member 102. Further, if empty spaces 102A and 102B are increased, it becomes difficult to flatly stack large sized sheets, which results in that the sheets cannot be assuredly conveyed into the image forming apparatus.
To counter the above problem, a sheet supplying cassette for an electro-photographic apparatus which could house small sized sheets, such as post cards, was presented in the Patent Gazette (see Patent Document 1).
According to Patent Document 1, provided are a first sheet supplying cassette to house the various sized sheets such as A3, A4, B4 and B5, and a second sheet supplying cassette to house post card sized sheets. When the sheets A3 to B5 are to be housed, the second sheet supplying cassette can be removed so that A3 to B5 sheets are housed in the first sheet supplying cassette, on the other hand, when post cards are to be housed, the second sheet supplying cassette is installed onto the first sheet supplying cassette so that post cards are housed in the second sheet supplying cassette.
[Patent Document 1] Japanese non-examined Patent Publication No. 11-59925
When the sheet supplying device is structured so as to house not only common sized sheets, such as sizes A3 to B5, but also a smaller size such as post cards, the art shown in Patent Document 1 must employ two sheet supplying cassettes. Thereby, when sheets which are frequently used, are housed, the second sheet supplying cassette is not necessary. Accordingly, a storage facility is necessary in which the second sheet supplying cassette can be kept without being damaged or soiled. Further an operator is required to install the second sheet supplying cassette onto the first sheet supplying cassette, and then to again remove the second sheet supplying cassette from the first sheet supplying cassette, which is troublesome.